What is the Beer-Lambert law?

Spectrophotometers are mainly used to measure the concentration of solutes in solution by measuring the amount of the light that is absorbed by the solution.

To estimate the amount of absorbed light, spectrophotometers use the Beer-Lambert law.

Beer-Lambert law describes the relation between the attenuation of light and the properties of the solution, where the light propagates:

A = εcl

where A is absorbance, c is the concentration, l is the path length and ε describes the absorption coefficient. 

Beer-Lambert law states that the absorbed light is proportional to the solute in a solution and the thickness of the solution. 

1. https://en.wikipedia.org/wiki/Beer%E2%80%93Lambert_law

2. https://www.edinst.com/blog/the-beer-lambert-law/